This invention concerns thermoformed products, and in particular open-topped plastic containers such as plant pots, formed with a rim which is slitted to receive a display insert.
Bedding plants are usually sold in rimmed pots or trays, and in the past, small display inserts printed with information such as the name of the plant, type, etc. were stuck into the soil in the pots. Such inserts were easily dislodged, removed, or switched to other containers by customers.
A display insert has been heretofore developed which is placed into a slit in the container rim with a locking action created by a barbed shape preventing removal.
In the thermoforming process, portions of a preheated plastic sheet material is stretched into a mold cavity in a tooling die, using plug assists and differential fluid pressure in a well known manner.
The containers so formed are subsequently cut free from the rest of the sheet in a trim station, using trim dies.
The regions surrounding portions of the sheet material to be formed into the container are clamped with clamping rings associated with each container mold cavity. A plug assist for each mold cavity is advanced into the sheet material to pre-stretch the material prior to application of the fluid pressure which is thereby applied to cause the material to be drawn into intimate contact with the mold cavities.
A through slot could possibly be molded to the rim during the thermoforming process by a mold feature, but this approach increases tooling costs since a special tooling feature must be provided for each cavity and a large number of cavities are typically employed, i.e., 24 or more cavities is typical for this type of product. Further more the need to mold in such a feature complicates the thermoforming process since only minimal space available in that area of the tooling.
Punching slots into the relatively thick rim after forming the containers requires a delicate punch and die set, prone to failure and also increasing the tooling costs.
More importantly, separate slugs would be produced by a punching process, and removing these slugs from the tooling is typically difficult. The presence of slugs which are not removed can create jams and other problems. Even if removed, disposal of the slugs is another burden.
As noted, the rim of the containers so formed is thicker than the body wall since a portion of the sheet material is stretched out during forming of the body while the rim is formed without stretching. This thick rim material is difficult to cut and thin knife blades will break easily if slitting is done in the trimming operation, to thus require a punch and die set.
Once slits are formed in the rim, the relatively thin plastic inserts are difficult to insert into a slit, particularly through an arcuate slit in the thick rim of a round container. If a punched out slot is formed to allow easier insertion, the expensive and delicate punch and die sets would be required. Also, slugs are formed creating problems as described above.
Furthermore, a high tonnage trim press would be required to perform the punching process, particularly when other steps are required to be done at the same time, such as to punch out bottom holes in the body portion.
It is the object of the present invention to provide an improved method and tooling to produce a thermoformed open-topped container having one or more slits in the rim thereof.
It is a further object to provide a thermoformed open topped product with slitted rim configuration which allows easy installation of a display insert into a slit in the rim.